MSc

The research project entitled “Evaluation of okra [Abelmoschus esculentus (L.) Moench] genotypes for yield and resistance to shoot and fruit borer, Earias vittella (Fab.)” was carried out in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani during the period 2011-2012. The study aimed at the evaluation of a collection of okra genotypes for shoot and fruit borer resistance and yield to identify high yielding shoot and fruit borer resistant genotypes, if available among them.

Thirty one genotypes of okra collected from different sources were evaluated for yield and resistance to shoot and fruit borer in a field experiment in randomized block design with three replications. Observations were recorded on 13 characters viz., days to 50% flowering, leaf axil bearing first fruit, number of primary branches, plant height, duration, number of fruits per plant, fruit weight, fruit length, fruit girth, yield per plant, shoot infestation, fruit infestation and number of larvae per 25 fruits.

Analysis of variance revealed significant differences among the genotypes for all the thirteen characters studied. Also the genotypes showed wide variation for the shoot and fruit borer infestation.

In this study, high values of PCV with correspondingly high values of GCV were observed for the characters viz., number of primary branches and number of fruits per plant which indicated the presence of substantial variability for these characters. High magnitude of heritability coupled with high genetic advance for the characters viz., yield per plant, number of fruits per plant, number of primary branches, fruit weight and fruit length suggested the scope for improvement of these characters through selection.

Both at phenotypic and genotypic levels, yield per plant showed high positive correlation with number of fruits per plant, fruit weight and fruit girth which implies that selection for these characters would lead to simultaneous improvement for yield per plant in okra.

In the present study, shoot and fruit borer resistance evaluation was done comparing the damage suffered by the accessions consequent to natural infestation under field condition. Significant differences were observed among the genotypes for all the damage parameters employed for resistance evaluation viz., percentage shoot infestation, percentage fruit infestation and larval count in 25 fruits. Fruit damage in terms of both percentage fruit infestation and larval count in 25 fruits was highest for T1 and lowest for T9. The genotypes T22 and T23 recorded the lowest percentage shoot infestation. Highest percentage shoot infestation was observed for genotypes T16 and T24. The genotypes T1, T2, T24 and T25 were found to suffer severe damage on all the three damage assessment criteria employed.
Fruit damage assessed based on percentage fruit infestation as well as larval count in fruits indicated T9 as the accession suffering the least fruit damage irrespective of the criterion employed for damage assessment. However, T9 was found to suffer significantly higher shoot damage in comparison with T22 and T23, the genotypes suffering least shoot damage. But the fruits of T22 and T23 were found to be severely attacked by the pest. Overall consideration of damage measurements indicate T9 as a worthwhile genotype with regard to shoot and fruit borer resistance. This notion is further supported by the result of the laboratory experiment conducted to get an insight into the larval feeding preferences which suggested T9 as the accession least preferred by the larvae for feeding.

Highly significant positive genotypic correlation between per cent fruit infestation and larval count in the fruits evident from the present study suggests that either of the fruit damage criteria may be employed for the evaluation of shoot and fruit borer resistance in okra.

T15 was the highest yielder among the accessions evaluated but found to suffer considerable damage from shoot and fruit borer infestation. On the other hand, T9 adjudged as the accession with the highest level of resistance to the pest was poor yielding. Combination breeding efforts utilizing T15, the highest yielder among the accessions evaluated and T9 as the shoot and fruit borer resistance source would hopefully lead to development of high yielding shoot and fruit borer resistant genotypes of okra.